/Engine/Source/Editor/VREditor/Public/UI/VREditorUISystem.h
Called to "preview" an input event to get a first chance at it.
void OnPreviewInputAction ( class [FEditorViewportClient](API\Editor\UnrealEd\FEditorViewportClient) & ViewportClient, [UViewportInteractor](API\Editor\ViewportInteraction\UViewportInteractor) * Interactor, const struct [FViewportActionKeyInput](API\Editor\ViewportInteraction\FViewportActionKeyInput) & Action, bool & bOutIsInputCaptured, bool & bWasHandled )